3rd Generation Partnership Project's (3GPP) long term evolution-advanced (LTE-A) wireless communication standard may be modified to add support for multi-user multiple-input multiple-output (MU-MIMO) systems. In LTE-A, each UE may be configured via radio resource control (RRC) signaling to be served by multiple aggregated component carriers (CCs), namely carrier aggregation (CA).
Carrier aggregation (CA) was introduced by LTE-A in order to support increased throughput, to prevent cost increase due to introduction of broadband radio-frequency (RF) elements and to provide compatibility with existing systems. Carrier aggregation enables data communications between a UE and an eNB through a plurality of carriers with same or different bandwidths.
Downlink control information (DCI) is used to carry scheduling assignments and other type of control information, which is transmitted on Physical Downlink Control Channel (PDCCH). It also carries a number of information fields such as for the modulation and coding scheme (MCS) and resource block assignment (RBA) and hopping resource allocation for data transmission. The need of scheduling a huge amount of UEs in a single TTI may incur large physical downlink control channel (PDCCH) requirement and available PDCCH resources may become a bottleneck for downlink scheduling in case of CA with large number of CCs (e.g. 32 CCs.). The design of the DCI on PDCCH for CA operation with a large amount of CCs is important with respect to overhead, efficiency, reliability, robustness, and complexity.